Discrete element analysis on aggregate breakage of unbound granular road materials

Adequate aggregate resistance to crushing and abrasion is crucial for good performance of unbound road layers, in particular when incorporating marginal aggregates in road construction. In this study, aggregate crushing in unbound granular materials (UGMs) is investigated experimentally with uniaxial compression tests, and numerically with discrete element method (DEM). A DEM model of UGMs subjected to uniaxial monotonic compression is implemented in a commercial DEM software, incorporating granular mechanics-based particle-contact and breakage laws. Based on comparison with the experimental findings, it is shown that the implemented model captures the UGMs behavior well including aggregate breakage characteristics. The model is used furthermore to evaluate aggregate crushing in UGMs subjected to cyclic loading representative for unbound road layers of low-volume roads. The feasibility of using the developed DEM approach for evaluating the implications of using marginal UGMs in unbound road layers and for optimizing structural design of those layers is discussed.